1. Field of the Invention
This invention relates to a cushioning material. More particularly, this invention relates to a cushioning material excellent in perviousness to air and in durability and usable as in automotive seats.
2. Description of Prior Arts
The seats heretofore used in automobiles and other vehicles have been preponderantly of the type being mounted on springs stretched taut in a frame a seat proper which comprises a cushion support member made of a plain weave of polyethylene or polypropylene tapes or of Palmlock material, a slab of polyurethane foam superposed on the cushion support member, and a surface coating material covering the surface of the slab of polyurethane foam. Since the component materials used in the seat of this type all lack perviousness to air, the seat passes air sparingly and fails to cause diffusion of the body heat of the rider or the ambient heat and compels the rider to feel uncomfortable. Further, since the cushioning material in the aforementioned seat proper is mainly made of polyurethane foam, when it is directly placed on the aforementioned springs, it will suffer the polyurethane foam to sustain cuts in the surface exposed to direct contact with the springs after prolonged use in that state. To avoid direct contact of the polyurethane foam with the springs, the seat proper is used by interposing between the polyurethane foam and the springs a cushion support material made of Palmlock material, non-woven fabric of polyethylene or hessian cloth (plain weave) of polyethylene or polypropylene. The use of this cushion support material not merely increases cost but also impairs the cushioning property of the seat proper. Moreover, this material prevents the seat proper from manifesting an ability to diffuse air reaching from below. Further, since polyurethane has lower elasticity to resist pressure than the cushion support material of fibers, the aforementioned slab of polyurethane foam is required to possess a large thickness to offer desirable cushioning property. The combined thickness of this slab of polyurethane foam and the cushion support material, therefore, gives a large height to the seat and consequently necessitates an increase in the height of the vehicle as a whole.
A cushioning material which is formed by integrally joining a lock material of short synthetic fibers as an upper seat layer to at least part of the surface of a substrate of Palmlock material (Published unexamined Japanese Patent Application No. SHO 52(1977)-101,164) has been known as a cushioning material enjoying relatively high perviousness to air. This cushioning material, however, is so heavy and hygroscopic as to render desired reduction in weight of the automobile difficult and jeopardize durability of the seat, mainly because its substrate is made of Palmlock material. Particularly this cushioning material has suffered from the disadvantage that, after a protracted use, it yields to the phenomenon called "permanent set in fatigue" and experiences loss of cushioning property and toughness desired. It is further defective in respect that it fails to offer desired perviousness to air.
One of the present inventors formerly developed a cushioning material highly pervious to air (U.S. Pat. Nos. 4,172,174, 4,298,418 and 4,386,041 and U.S. Ser. No. 292,907). One of his inventions covering this cushioning material relates to a reinforced cushioning material comprising a compression molded body of drafted three-dimensionally crimped filament mass of a synthetic fiber in which the crimped filaments are of stable length and randomly-oriented and the contact points between each of the filaments are bonded with an adhesive, said body having isolated zones in which the crimped filament is further crimped in situ into various shapes formed by partially expanding and compressing the filament crimps in said zones, and said zones being distributed throughout the reinforced portion of said body, being oriented in the same direction, and having increased density in the degree of entanglement and the number of contact points.
By taking notice of the fact that this cushioning material, used in the vehicular seat, exhibits high perviousness to air, the inventor further developed a seat capable of being air conditioned with cool air or warm air introduced into the interior of the seat (Published unexamined Japanese Utility Model Application Nos. SHO 55(1980)-148,449, SHO 57(1982)-90,661 through 90,664, SHO 57(1982)-142,945 through 142,946 and SHO 57(1982)-146,558).
The aforementioned cushioning material, however, has the disadvantage that the perviousness to air is lowered when the bulk density of the cushioning material is increased for the purpose of improving the durability and this durability is lowered when the bulk density is lowered for the purpose of improving the perviousness to air.
An object of this invention, therefore, is to provide a novel cushioning material.
Another object of this invention is to provide a cushioning material excellent in perviousness to air and in durability and usable such as in automotive seats.